Lithium Atom Surface Diffusion and Delocalized Deposition Propelled by Atomic Metal Catalyst toward Ultrahigh-Capacity Dendrite-Free Lithium Anode.

Lithium metal anode possesses overwhelming capacity and low potential but suffers from dendrite growth and pulverization, causing short lifespan and low utilization. Here, a fundamental novel insight of using single-atomic catalyst (SAC) activators to boost lithium atom diffusion is proposed to realize delocalized deposition. By combining electronic microscopies, time-of-flight secondary ion mass spectrometry, theoretical simulations, and electrochemical analyses, we have unambiguously depicted that the SACs serve as kinetic activators in propelling the surface spreading and lateral redistribution of the lithium atoms for achieving dendrite-free plating morphology. Under the impressive capacity of 20 mA h cm-2, the Li modified with SAC-activator exhibits a low overpotential of ∼50 mV at 5 mA cm-2, a long lifespan of 900 h, and high Coulombic efficiencies during 150 cycles, much better than most literature reports. The so-coupled lithium-sulfur full battery delivers high cycling and rate performances, showing great promise toward the next-generation lithium metal batteries.

In Situ X-ray Absorption Spectroscopic Investigation of the Capacity Degradation Mechanism in Mg/S Batteries.

The Mg/S battery is attractive because of its high theoretical energy density and the abundance of Mg and S on the earth. However, its development is hindered by the lack of understanding to the underlying electrochemical reaction mechanism of its charge-discharge processes. Here, using a unique in situ X-ray absorption spectroscopic tool, we systematically study the reaction pathways of the Mg/S cells in Mg(HMDS)2-AlCl3 electrolyte. We find that the capacity degradation is mainly due to the formation of irreversible discharge products, such as MgS and Mg3S8, through a direct electrochemical deposition or a chemical disproportionation of intermediate polysulfide. In light of the fundamental understanding, we propose to use TiS2 as a catalyst to activate the irreversible reaction of low-order MgS x and MgS, which results in an increased discharging capacity up to 900 mAh·g-1 and a longer cycling life.

Superfast Zincophilic Ion Conductor Enables Rapid Interfacial Desolvation Kinetics for Low-Temperature Zinc Metal Batteries.

Low-temperature rechargeable aqueous zinc metal batteries (AZMBs) as highly promising candidates for energy storage are largely hindered by huge desolvation energy barriers and depressive Zn2+ migration kinetics. In this work, a superfast zincophilic ion conductor of layered zinc silicate nanosheet (LZS) is constructed on a metallic Zn surface, as an artificial layer and ion diffusion accelerator. The experimental and simulation results reveal the zincophilic ability and layer structure of LZS not only promote the desolvation kinetics of [Zn(H2O)6]2+ but also accelerate the Zn2+ transport kinetics across the anode/electrolyte interface, guiding uniform Zn deposition. Benefiting from these features, the LZS-modified Zn anodes showcase long-time stability (over 3300 h) and high Coulombic efficiency with ≈99.8% at 2 mA cm-2, respectively. Even reducing the environment temperature down to 0 °C, ultralong cycling stability up to 3600 h and a distinguished rate performance are realized. Consequently, the assembled Zn@LZS//V2O5-x full cells deliver superior cyclic stability (344.5 mAh g-1 after 200 cycles at 1 A g-1) and rate capability (285.3 mAh g-1 at 10 A g-1) together with a low self-discharge rate, highlighting the bright future of low-temperature AZMBs.

Interfacial "Single-Atom-in-Defects" Catalysts Accelerating Li+ Desolvation Kinetics for Long-Lifespan Lithium-Metal Batteries.

The lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li+ , Li0 nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co1- x S embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li+ solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO4 cathode, the full cell (10.7 mg cm-2 ) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications.

Toward Dendrite-Free Metallic Lithium Anodes: From Structural Design to Optimal Electrochemical Diffusion Kinetics.

Lithium metal anodes are ideal for realizing high-energy-density batteries owing to their advantages, namely high capacity and low reduction potentials. However, the utilization of lithium anodes is restricted by the detrimental lithium dendrite formation, repeated formation and fracturing of the solid electrolyte interphase (SEI), and large volume expansion, resulting in severe "dead lithium" and subsequent short circuiting. Currently, the researches are principally focused on inhibition of dendrite formation toward extending and maintaining battery lifespans. Herein, we summarize the strategies employed in interfacial engineering and current-collector host designs as well as the emerging electrochemical catalytic methods for evolving-accelerating-ameliorating lithium ion/atom diffusion processes. First, strategies based on the fabrication of robust SEIs are reviewed from the aspects of compositional constituents including inorganic, organic, and hybrid SEI layers derived from electrolyte additives or artificial pretreatments. Second, the summary and discussion are presented for metallic and carbon-based three-dimensional current collectors serving as lithium hosts, including their functionality in decreasing local deposition current density and the effect of introducing lithiophilic sites. Third, we assess the recent advances in exploring alloy compounds and atomic metal catalysts to accelerate the lateral lithium ion/atom diffusion kinetics to average the spatial lithium distribution for smooth plating. Finally, the opportunities and challenges of metallic lithium anodes are presented, providing insights into the modulation of diffusion kinetics toward achieving dendrite-free lithium metal batteries.

Single-Atomic Catalysts Embedded on Nanocarbon Supports for High Energy Density Lithium-Sulfur Batteries.

Lithium-sulfur batteries are among the most promising candidates for next-generation energy-storage systems due to its high theoretical energy density. However, the shuttle effect of polysulfides and sluggish reaction kinetics severely hinder the development of practical Li-S batteries. Merely depending on an adsorption strategy to resist the shuttle effect is insufficient to boost the overall electrochemical conversion reaction. Recently, single atom catalysts (SACs) have been used to solve this problem by decreasing the energy barriers of sulfur-species interconversion and Li2 S decomposition. Herein, the research progress made in using SACs in Li-S batteries is discussed, focusing on their functions and catalytic mechanism. The challenges and prospects for future application of SACs in electrochemical energy-storage systems are also discussed.

Multi-ion Modulated Single-Step Synthesis of a Nanocarbon Embedded with a Defect-Rich Nanoparticle Catalyst for a High Loading Sulfur Cathode.

Oxygen defect-rich iron oxide (ODFO) nanoparticle catalyst on nanocarbon is in situ synthesized with the assistance of multi-ion modulation in one pot. The nanoparticle catalyst is employed to propel electrochemical kinetics in lithium/sulfur batteries. Electrochemical analysis and theoretical simulation evidently verify the critical role of defect sites on catalyzing conversion reactions of sulfur species and reducing energy barriers. As a consequence, the ODFO-enhanced sulfur cathode exhibits a high specific capacity of 1489 mA h g-1 at 0.1 C, an excellent rate performance of 644 mA h g-1 at 10 C, and a superior cycling stability with an average capacity fading rate of as low as 0.055% per cycle under an ultrahigh rate of 10 C. More importantly, even with a high sulfur loading of 11.02 mg cm-2, the Li/S cell can still deliver an areal capacity of 8.7 mA h cm-2 at 0.5 C (9.23 mA cm-2). Such performance is the highest among reported metal oxide-catalyzed sulfur cathodes. This work opens a new route to boosting conversion reaction kinetics by introduction of active oxygen defect sites in electrodes of various emerging ultrafast batteries.

Hierarchical Sulfur-Doped Graphene Foam Embedded with Sn Nanoparticles for Superior Lithium Storage in LiFSI-Based Electrolyte.

Lithium-ion batteries based on tin (Sn) anode have the advantage of high energy density at a reasonable cost. However, their commercialization suffers from rapid capacity fading caused by active material aggregation, huge volumetric change, and continuous formation/deformation of solid-electrolyte interphase (SEI). Herein, we report an anode made of nanosized metallic Sn particles embedded in a hierarchically porous sulfur-doped graphene foam (Sn@3DSG). In this design, the sulfur-doped graphene foam provides abundant active defect sites to facilitate the rapid lithium-ion diffusion from outside to inside the Sn nanoparticles. Meanwhile, the hierarchical pores resulting from the self-assembly of graphene and evaporation of nanosized metallic Zn provide sufficient space to hold the volumetric changes of Sn. Owing to these merits, the as-prepared Sn electrode exhibits an excellent lithiated capacity (1272 mA h g-1 at 200 mA g-1) and high-rate performance (345 mA h g-1 at 2000 mA g-1) in the LiFSI-based electrolyte. It is also discovered that a LiF-Li3N-rich SEI layer is formed on the surface of the Sn electrode in a LiFSI-based electrolyte, which is beneficial for enhancing the electrode's cycling stability. Our work shows great promise of composite Sn anodes for future high-energy-density lithium-ion batteries.